Preparation method of quantum dot compound and quantum dot light-emitting device containing quantum dot compound
By coating the surface of quantum dots with an oxide shell and using alternating acidic and alkaline methods to drop silicon and aluminum sources, the stability problem of quantum dot materials was solved, and high efficiency and stability of quantum dot light-emitting devices were achieved.
Patent Information
- Application Number
- CN202511539576.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-27
- Publication Date
- 2026-02-17
AI Technical Summary
When quantum dot materials come into close contact with LED blue light chips, their resistance to water, oxygen, and high temperatures is insufficient, which affects their optical performance.
By coating the surface of quantum dots with a dense thin layer and a dense thick layer of oxide shell, and by alternately adding silicon and aluminum sources under acidic and alkaline conditions, a uniform oxide shell layer is formed, thereby improving the stability of quantum dots.
The optical stability and aging performance of the quantum dot light-emitting device were enhanced, maintaining high initial efficiency and improving stability during later aging.
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Figure CN121537952A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of quantum dot composite technology, and more specifically, to a method for preparing a quantum dot composite and a quantum dot light-emitting device containing the composite. Background Technology
[0002] With the advancement of technology, people's performance requirements for display devices are gradually increasing, and display devices using quantum dot materials, which have narrow half-width and high luminous intensity, are particularly favored. By adjusting the emission wavelength and half-width of quantum dots and directly encapsulating the quantum dot material on LED blue light chips, a higher color gamut can be achieved, thus meeting the needs of different customers. In this approach, because the quantum dot material is in close contact with strong blue light, it typically requires extremely high resistance to water and oxygen, high temperatures, and blue light stability. Therefore, it is necessary to first coat the quantum dots with oxides and then use silicone encapsulation to further improve stability for related applications. Summary of the Invention
[0003] The purpose of this application is to provide a method for preparing quantum dot composites and a quantum dot light-emitting device containing the composites, so as to solve the problem of insufficient optical stability of quantum dot composites.
[0004] A first aspect of this application provides a method for preparing a quantum dot composite, the method comprising: S1, preparing an alcohol dispersion of quantum dots; S2, preparing a mixture of alcohol and acid in a container, the pH of the mixture being 2-5, adding the alcohol dispersion of quantum dots to the container and mixing it evenly, and adding at least one of a silicon source and an aluminum source dropwise, thereby coating the surface of the quantum dots with an oxide shell of a first thickness; S3, adding an alkaline substance dropwise to the container to make the final pH of the reaction system 8-12, and simultaneously adding at least one of a silicon source and an aluminum source dropwise during the addition of the alkaline substance, thereby further coating the surface of the quantum dots with an oxide shell of a second thickness, the first thickness being less than the second thickness.
[0005] Optionally, the first thickness is 2-5 nm and the second thickness is 8-25 nm.
[0006] Optionally, the ligands on the quantum dot surface include one or more of mercaptoethanol, 3-mercapto-1-propanol, 4-mercapto-1-butanol, or 2-mercaptoethylamine hydrochloride.
[0007] Optionally, the alcohol in the quantum dot alcohol dispersion is selected from at least one of ethanol, ethylene glycol, methanol, butanol, and octanol, and the alcohol in the mixture is selected from at least one of ethanol, ethylene glycol, methanol, butanol, and octanol.
[0008] Optionally, the silicon source is selected from at least one of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and vinyltrimethoxysilane, and the aluminum source is selected from at least one of aluminum nitrate, aluminum isopropoxide, aluminum sec-butoxide, and aluminum triethanolamine.
[0009] Optionally, the acid is selected from at least one of nitric acid, hydrochloric acid, sulfuric acid, acetic acid, and trifluoroacetic acid, and the alkaline substance is selected from at least one of ammonia water, tetramethylammonium hydroxide aqueous solution, and tetraethylammonium hydroxide aqueous solution.
[0010] Optionally, the volume ratio of the quantum dot alcohol dispersion to the mixture is 1:10-1:50, and the concentration of quantum dots in the quantum dot alcohol dispersion is 30-50 mg / mL.
[0011] Alternatively, the OH group of an alkaline substance - The dropping rate was 0.5-5 μmol / min.
[0012] Optionally, the dropping rate of the silicon source, calculated based on the elemental silicon, is 5-1000 μmol / min; and the dropping rate of the aluminum source, calculated based on the elemental aluminum, is 5-500 μmol / min.
[0013] A second aspect of this application provides a quantum dot light-emitting device comprising a quantum dot composite prepared by any of the quantum dot composite preparation methods described above.
[0014] The above technical solution involves a quantum dot composite comprising quantum dots, a dense thin oxide shell coated on the quantum dots (synthesized under acidic conditions), and a dense thick oxide shell coated on the thin oxide shell (synthesized under alkaline conditions). Applying this quantum dot composite to light-emitting devices such as LED chips can improve the stability of these devices, thereby enabling better optical applications. Attached Figure Description
[0015] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:
[0016] Figure 1 This is a schematic diagram illustrating the preparation principle of a quantum dot composite according to a typical embodiment of this application. Detailed Implementation
[0017] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.
[0018] A first aspect of this application provides a method for preparing a quantum dot composite, the method comprising: S1, preparing an alcohol dispersion of quantum dots; S2, preparing a mixture of alcohol and acid in a container, the pH of the mixture being 2-5, adding the alcohol dispersion of quantum dots to the container and mixing it evenly, and adding at least one of a silicon source and an aluminum source dropwise, thereby coating the surface of the quantum dots with an oxide shell of a first thickness; S3, adding an alkaline substance dropwise to the container to make the final pH of the reaction system 8-12, and simultaneously adding at least one of a silicon source and an aluminum source dropwise during the addition of the alkaline substance, thereby further coating the surface of the quantum dots with an oxide shell of a second thickness, the first thickness being less than the second thickness.
[0019] The dropwise addition method allows for the slow hydrolysis of silicon and aluminum sources on the quantum dot surface, coating them with an oxide shell. This helps reduce the generation of blank oxide particles from the rapid hydrolysis of silicon and aluminum sources, thus improving yield. The thiol groups on the surface of the ligand-exchanged quantum dot composite are extremely unstable in an alkaline environment, easily dissociating and causing structural changes. Therefore, initially setting acidic conditions for coating can reduce damage to the surface of the quantum dot composite, maintaining relatively high optical performance. Secondly, the relatively slow hydrolysis rate of silicon and aluminum sources under acidic conditions is conducive to the formation of a uniform and dense silicon-aluminum oxide shell on the outside of the quantum dot composite, thereby improving the material's resistance to water and oxygen. However, the acidic conditions further inhibit the continued hydrolysis of silicon and aluminum sources, ultimately resulting in only a thin oxide shell on the surface of the quantum dot composite. But with continued coating under alkaline conditions, the hydrolysis rate of silicon and aluminum sources increases, allowing for the formation of an oxide shell of the target thickness on top of the thin oxide shell. Combining these coating methods maximizes the material's luminescence efficiency while improving its optical stability.
[0020] The pH ranges in S1 and S3 can be adjusted according to the types of silicon and aluminum sources actually used. In some embodiments, the pH range of S1 can be 3-4, and the pH range of S3 can be 10-11. In some embodiments, the quantum dots are core-shell quantum dots, and the core of the quantum dots can be selected from group II-VI compounds, group III-VI compounds, group I-III-VI compounds, group III-V compounds, group III-II-V compounds, group IV-VI compounds, group IV elements, group IV compounds, and combinations thereof. In some embodiments, the full width at half maximum (FWHM) of the emission peak of the fluorescence emission spectrum of the core-shell quantum dots can be less than or equal to about 45 nm, or less than or equal to about 40 nm, or less than or equal to about 30 nm. In some embodiments, the fluorescence peak position of the core-shell quantum dots is selected from 450-660 nm.
[0021] In some embodiments, the mixture contains water, which may be derived from alcohol and / or acid, thereby facilitating pH adjustment.
[0022] In some embodiments, during the addition of the alkaline substance, a silicon source and an aluminum source (or a single silicon source or aluminum source) are added simultaneously. The alkaline substance is added first, followed by the addition of the silicon source and the aluminum source (or a single silicon source or aluminum source). During the addition of the silicon source and the aluminum source (or a single silicon source or aluminum source), the pH of the reaction system gradually increases. In some embodiments, the dispersion medium for the silicon source and the aluminum source is independently an alcohol.
[0023] In some embodiments, after the addition of S2 is completed, the reaction continues for a certain period of time (e.g., 0.1-5 hours) to complete the coating of the oxide shell of the first thickness.
[0024] In some embodiments, after the addition of S3 is completed, the reaction continues for a certain period of time (e.g., 1-24 hours) to complete the coating of the oxide shell of the second thickness.
[0025] In some embodiments, the reaction temperature of the shell coating (S1 and / or S2) is room temperature, which can be 15-40°C.
[0026] In some embodiments, the first thickness is 2-5 nm, and the second thickness is 8-25 nm. A thicker coating can be applied without reducing fluorescence efficiency.
[0027] In some embodiments, the surface ligands of the quantum dots are selected from one or more of mercaptoethanol, 3-mercapto-1-propanol, 4-mercapto-1-butanol, or 2-mercaptoethylamine hydrochloride, providing alcohol solubility for the quantum dots. In some embodiments, the method for preparing an alcohol dispersion of quantum dots includes first preparing oil-soluble quantum dots, then performing ligand exchange on the oil-soluble quantum dots, such as using alcohol-soluble ligands, to obtain alcohol-soluble quantum dots, thereby allowing the quantum dots to be stably dispersed in alcohol.
[0028] In some embodiments, the alcohol in the quantum dot alcohol dispersion is selected from at least one of ethanol, ethylene glycol, methanol, butanol, and octanol, and the alcohol in the mixture is selected from at least one of ethanol, ethylene glycol, methanol, butanol, and octanol.
[0029] In some embodiments, the silicon source is selected from at least one of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane, and vinyltrimethoxysilane, and the aluminum source is selected from at least one of aluminum nitrate, aluminum isopropoxide, aluminum sec-butoxide, and aluminum triethanolamine.
[0030] In some embodiments, the acid is selected from at least one of nitric acid, hydrochloric acid, sulfuric acid, acetic acid, and trifluoroacetic acid, and the alkaline substance is selected from at least one of ammonia, tetramethylammonium hydroxide aqueous solution, and tetraethylammonium hydroxide aqueous solution.
[0031] In some embodiments, the volume ratio of the quantum dot alcohol dispersion to the mixture is 1:10 to 1:50.
[0032] In some preferred embodiments, the concentration of quantum dots in the alcohol dispersion is 30-50 mg / mL. A suitable quantum dot concentration is more conducive to the formation of a uniform shell.
[0033] In some embodiments, the OH- of alkaline substances - The dropping rate is 0.5-5 μmol / min. When the alkaline substance is ammonia, the dropping rate is calculated based on the ionization constant. In some embodiments, the dropping rate for the silicon source, calculated based on silicon elemental concentration, is 5-1000 μmol / min. In some embodiments, the dropping rate for the aluminum source, calculated based on aluminum elemental concentration, is 5-500 μmol / min. The aforementioned dropping rates are related to the concentration of the alcohol dispersion of quantum dots and can be adjusted according to actual needs.
[0034] In some embodiments, the ratio of the amount of alkaline substance added (calculated in mmol) to the absorbance (OD, optical density) of the quantum dots in the alcohol dispersion of the quantum dots is 0.001:1-0.01:1. In some embodiments, in S1, the added acid (H + The molar ratio of the alkaline substance added to the silicon source (silicon element) and the sum of the aluminum source (aluminum element) is 0.0001-0.01:1. In some embodiments, in S2, the OH- of the alkaline substance added... - The molar ratio of silicon source (silicon element) to the sum of aluminum source (aluminum element) is 1:50.
[0035] In some embodiments, after the shell coating is completed, a precipitant is added to the product system, and then the precipitate is separated and purified to obtain the quantum dot complex. The separation and purification method can refer to the prior art.
[0036] A second aspect of this application provides a quantum dot light-emitting device, the quantum dot light-emitting device comprising the quantum dot composite as described above. Applying this quantum dot composite to light-emitting devices such as LED chips can improve the stability of the quantum dot light-emitting device, thereby achieving better optical applications.
[0037] The aforementioned quantum dot light-emitting device can be used for display or lighting. In some embodiments, the quantum dot light-emitting device is a display device, with the quantum dot composite located above the LED chip to perform light conversion. In some embodiments, the quantum dot light-emitting device further includes phosphor.
[0038] The implementation methods are described in more detail below with reference to specific embodiments. However, these are exemplary examples of the content of this application, and the content of this application is not limited thereto.
[0039] Example 1
[0040] Add 0.2 mL of mercaptoethanol to 1.5 mL of 133 mg / mL quantum dot toluene solution (CdSe type, OD of 40 at 450 nm), sonicate for 10 min to perform ligand exchange, and disperse the precipitate in 5 mL of anhydrous ethanol after high-speed centrifugation to obtain a quantum dot ethanol dispersion.
[0041] Prepare a 250 mL single-necked flask and add 50 mL of an ethanol-water aqueous solution with a volume ratio of 3:1. Slowly add approximately 0.5 mL of 0.01 M hydrochloric acid-ethanol solution to establish an acidic system with pH=4. Slowly add the quantum dot ethanol dispersion to this system while continuously stirring. Dissolve 4 mmol of aluminum isopropoxide in 10 mL of ethanol, and then add 1 mL of tetraethyl orthosilicate to prepare the silicon and aluminum source alcohol dropping solution required for coating the thin oxide shell. Add this dropping solution to the reaction system at a rate of 0.5 mL / min, and continue the reaction for 1 h after the dropping is completed.
[0042] 12 mmol of aluminum isopropoxide was dissolved in 30 mL of ethanol, and then 6 mL of tetraethyl orthosilicate was added to prepare the silicon and aluminum source alcohol dropping solution required for coating a thick oxide shell. This dropping solution was slowly added dropwise at a rate of 0.01 mL / min for approximately 0.4 mL of ammonia-ethanol solution (0.1 M) to gradually transition the system from an acidic system to an alkaline system with pH=10. During this process, the silicon and aluminum source alcohol dropping solution was continuously added dropwise at a rate of 0.9 mL / min. After the addition was completed, the reaction continued for 6 hours. Ethyl acetate was added as a precipitant to the product system, and the mixture was centrifuged. The supernatant was discarded, and the precipitate was dispersed in toluene or octane to obtain a quantum dot composite coated with silicon and aluminum oxide. In the preparation of LED devices, the composite solvent was evaporated and mixed evenly with 5 g of silicone. The mixture was then applied to an LED chip using a dispensing machine and cured by baking to obtain the final quantum dot LED light-emitting device.
[0043] Example 2
[0044] Add 0.2 mL of mercaptoethanol to 1.5 mL of 133 mg / mL quantum dot toluene solution (CdSe type, OD of 40 at 450 nm), sonicate for 10 min to perform ligand exchange, and disperse the precipitate in 5 mL of anhydrous ethanol after high-speed centrifugation to obtain a quantum dot ethanol dispersion.
[0045] Prepare a 250 mL single-necked flask and add 70 mL of an ethanol-water aqueous solution with a volume ratio of 6:1. Slowly add approximately 0.7 mL of 0.1 M hydrochloric acid-ethanol solution to establish an acidic system with pH=3. Slowly add the quantum dot ethanol dispersion to this system while continuously stirring. Dissolve 1 mmol of aluminum isopropoxide in 10 mL of ethanol, and then add 0.2 mL of tetraethyl orthosilicate to prepare the silicon and aluminum source alcohol dropping solution required for coating the thin oxide shell. Add this dropping solution to the reaction system at a rate of 0.1 mL / min, and stop the reaction after 10 min.
[0046] 2 mmol of aluminum isopropoxide was dissolved in 30 mL of ethanol, and then 2 mL of tetraethyl orthosilicate was added to prepare the silicon and aluminum source alcohol dropping solution required for coating a thick oxide shell. This dropping solution was slowly added dropwise at a rate of 0.01 mL / min for approximately 0.7 mL of ammonia-ethanol solution (0.1 M) to gradually transition the system from an acidic system to an alkaline system with pH=11. During this process, the silicon and aluminum source alcohol dropping solution was continuously added dropwise at a rate of 0.457 mL / min. After the addition was completed, the reaction continued for 2 hours. Ethyl acetate was added as a precipitant to the product system, and the mixture was centrifuged. The supernatant was discarded, and the precipitate was dispersed in toluene or octane to obtain a quantum dot composite coated with silicon and aluminum oxide. In the preparation of LED devices, the composite solvent was evaporated and mixed evenly with 5 g of silicone. The mixture was then applied to an LED chip using a dispensing machine and cured by baking to obtain the final quantum dot LED light-emitting device.
[0047] Comparative Example 1
[0048] The difference from Example 1 is that the quantum dot composite was prepared by only acid coating according to the method of Example 1.
[0049] Comparative Example 2
[0050] The difference from Example 1 is that the quantum dot complex was prepared by simply coating under alkaline conditions according to the method of Example 1.
[0051] Aging performance test
[0052] After curing, the quantum dot LED (4014) light-emitting device was removed and placed in an oven at 65 ℃ and RH 95% for aging at a current of 60mA (450nm). The light-emitting device was removed periodically and its optical performance was tested using an integrating sphere. The aging performance test results are shown in Table 1 below.
[0053] Table 1
[0054] Aging time 0h 24h 72h 168h 504h 1008h Example 1 72.31% 72.25% 72.15% 72.23% 72.28% 71.56% Example 2 71.95% 71.58% 69.45% 68.42% 67.44% 66.23% Comparative Example 1 74.52% 71.38% 68.42% 63.79% 58.27% 52.93% Comparative Example 2 67.22% 65.56% 65.25% 63.96% 61.25% 58.34%
[0055] The aging data above shows that Comparative Example 1, which was coated under acid conditions, had very poor aging performance of the light-emitting device. Comparative Example 2, which was coated under alkaline conditions, had low initial efficiency and poor aging performance. Examples 1 and 2, which were coated under acid conditions first and then under alkaline conditions, can maintain high initial efficiency and ensure good aging stability in the later stages.
[0056] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.
Claims
1. A method for preparing a quantum dot complex, characterized by, The preparation method comprises: S1, preparing an alcohol dispersion liquid of quantum dots; S2, preparing a mixed solution of alcohol and acid in a container, the pH of the mixed solution being 2-5, adding the alcohol dispersion liquid of quantum dots in the container and mixing uniformly, and dropping at least one of a silicon source and an aluminum source, so as to coat a first thickness of oxide shell on the surface of the quantum dots; S3, dropping an alkaline substance in the container so that the final pH of the reaction system is 8-12, and at the same time dropping at least one of a silicon source and an aluminum source in the process of dropping the alkaline substance, so as to continue coating a second thickness of oxide shell on the surface of the quantum dots, the first thickness being less than the second thickness.
2. The method of claim 1, wherein the quantum dot composite is prepared by the steps of: The first thickness is 2-5 nm, and the second thickness is 8-25 nm.
3. The method for preparing the quantum dot composite according to claim 1, characterized in that, The ligand on the surface of the quantum dots comprises one or more of mercaptoethanol, 3-mercapto-1-propanol, 4-mercapto-1-butanol or 2-mercaptoethylamine hydrochloride.
4. The method for preparing the quantum dot composite according to claim 1, characterized in that, The alcohol in the alcohol dispersion liquid of quantum dots is selected from at least one of ethanol, ethylene glycol, methanol, butanol and octanol, and the alcohol in the mixed solution is selected from at least one of ethanol, ethylene glycol, methanol, butanol and octanol.
5. The method for preparing the quantum dot composite according to claim 1, characterized in that, The silicon source is selected from at least one of tetraethyl orthosilicate, tetramethyl orthosilicate, methyltrimethoxysilane, methyltriethoxysilane and vinyltrimethoxysilane, and the aluminum source is selected from at least one of aluminum nitrate, aluminum isopropoxide, aluminum sec-butoxide and aluminum triethoxide.
6. The method for preparing the quantum dot composite according to claim 1, characterized in that, The acid is selected from at least one of nitric acid, hydrochloric acid, sulfuric acid, acetic acid and trifluoroacetic acid, and the alkaline substance is selected from at least one of ammonia water, aqueous tetramethylammonium hydroxide solution and aqueous tetraethylammonium hydroxide solution.
7. The method for preparing the quantum dot composite according to claim 1, characterized in that, The volume ratio of the alcohol dispersion liquid of quantum dots to the mixed solution is 1:10-1:50, and the concentration of quantum dots in the alcohol dispersion liquid of quantum dots is 30-50 mg / mL.
8. The method for preparing the quantum dot composite according to claim 1 or 7, characterized in that, The OH of the basic substance - The dropwise addition rate is 0.5-5 μmol / min.
9. The method for preparing the quantum dot composite according to claim 1 or 7, characterized in that, The dropping speed of the silicon source calculated according to the silicon element is 5-1000 μmol / min, and the dropping speed of the aluminum source calculated according to the aluminum element is 5-500 μmol / min.
10. A quantum dot light-emitting device, characterized in that, The quantum dot light-emitting device comprises the quantum dot composite prepared by the quantum dot composite preparation method according to any one of claims 1 to 9.